Dual circulation aeration apparatus



May 29, 1956 A. c. DAMAN 2,747,733

DUAL CIRCULATION AERATION APPARATUS Filed July 18, 1950 5 Sheets-Sheet 1 4 F IG.- 2

g JNVENTOR. u Arthur 0. Damon ATTORN EY May 29, 1956 A. C. DAMAN DUAL CIRCULATION AERATION APPARATUS Filed July 18, 1950 5 Sheets-Sheet 2 ZZH 45 INVENTOR. Arthur G. Damon kza ng w ATTORNEY May 29, 1956 A. c. DAMAN 2,747,733

DUAL CIRCULATION AERATION APPARATUS Filed July 18, 1950 5 Sheets-Sheet 3 Arfhur 0. Damon ATTORNEY May 29, 1956 A. c. DAMAN DUAL CIRCULATION AERATION APPARATUS 5 Sheets-Sheet 4 Filed July 18, 1950 INVENTOR.

Arthur 0. Damon ATTORNEY May 29, 1956 A. c. DAMAN 2,747,733

DUAL CIRCULATION AERATION APPARATUS Filed July 18, 1950 5 Sheets-Sheet 5 INVENTOR. Arthur 0. Damon ATTORNEY United Stats DUAL CIRCULATION AERATION APPARATUS Application July 18, 1950, Serial No. 174,472

9 Claims. (Cl. 209-468) This invention relates to froth flotation apparatus, and more particularly relates to a multicell flotation machine adapted to perform a variety of treatments by simple variations in its structural form.

It has been customary in designing froth flotation equipment for commercial treatments to provide standardized cell designs in a variety of sizes. However, in usual plant practice, certain of the cells are used for a rougher operation, whereas others will be operated as cleaner cells. Obviously if the rougher cells are designed to operate under optimum conditions, the cleaner cells are relatively inefl'icient, and vice versa.

The present invention recognizes the inefliciency of earlier type machines and provides a machine which by simple and easy changes in control features permits selective variation of circulation, or selective variation of aeration, as required. In addition, the machine design permits selective changes from a hog-trough type of operation to an individual cell type of operation as required. 7

It is an object of this invention to provide simple, durable and efficient flotation apparatus which is well suited to perform both rougher and cleaner operations in froth flotation treatments.

Another object of the invention is to provide froth flotation apparatus that provides a circulatory movement of pulp that may be selectively varied to suit different treatment requirements.

Still another object of the invention is to provide froth flotation apparatus that provides a selective control of the aeration in the individual cells of the machine.

Yet another object of the invention is to provide a novel type of aerating action in a froth flotation treatment in which coarse feed of the pulp is aerated and agitated in one zone while fines of the feed are aerated and agitated in a second zone.

Other objects reside in novel details of construction and novel combinations and arrangements of parts, all of which will ,be fully described in the course of the following description.

The practice of the invention will be best understood by reference to the accompanying drawings. In the drawings in the several views of which like parts have been designated similarly,

Fig. l is a fragmentary top plan view of the first two cells of a multiple-cell flotation machine embodying features of the present invention;

Fig. 2 is a fragmentary front elevation of the two cells shown in Fig. 1;

Fig. 3 is a fragmentary top plan view of another two cells of a multiple-cell flotation machine embodying features of the present invention;

Fig. 4 is a fragmentary front elevation of the two cells shown in Fig. 3;

Fig. 5 is a fragmentary top plan view'of another two cells of a multiple-cell flotation machine embodying features of the present invention;

Fig. 6 is a fragmentary front elevation of the two cells atent O ice shown in Fig. 5, partially broken away to show the arrangement of interior parts; and

Fig. 7 is a section taken along the line 77, Fig. 2.

While the multiple-cell features of the present invention have been illustrated in three, two-cell groups constituting a six cell machine, it will be appreciated that any number of cells of any given type may be combined to form a single machine. In such event, the feed arrangement shown in the first cell of Fig. 2, and the final discharge arrangement shown in Fig. 6 will be utilized in the first and last cells of the machine.

As illustrated, in Figs. 1 and 2, the flotation apparatus comprises a tank T consisting of a front wall section 12 having a froth overflow lip 13, an end wall 14, a partitioning member 15 spaced from and substantially parallel to wall 14 and defining therewith a feed inlet compartment 16, through which a short, tubular feed inlet conduit 17 extends, and connects with another conduit 18 for delivery of pulp directly onto an impeller, such as is illustrated by impeller 19 or an agitator of the type shown at 21 in Fig. 6. A rear wall 22 and a second partitioning member or end wall 23 complete the enclosure of the first cell C within tank T. An adjustable weir 24 controlled by a screw 25 or other actuating mechanism is located in the next feed compartment 16' between walls 23 and 15 to control the overflow of pulp to the feed conduit 18 of the next cell C of the machine. Some of the heavier sands which do not suspend readily in the liquid of the pulp and normally would tend to collect in the bottom portion of'the cell are discharged through a venturi outlet 26 for delivery into the cell C.

Each of the cells is provided in its lower portion with a baffle structure comprising a bowl-like liner section 28, 28 or 28*, and a series of upstanding baffles 29,29 or 29*, disposed in substantially radial arrangement within the enclosure. journaled in suitable bearings 32, 52 or 32 is supported from the superstructure 33, 33 or 33 mounted on the top surface of tank T, and is driven by motor 34, 34 or 34 through the intermediary of a belt transmission system 35, 35 or 35*. Each shaft carries at least one impeller member submerged in the pulp body in the tank, the details of which vary in different cells, all of which will be fully described in the following description. A rotary froth scraper or skimmer 37, is mounted adjacent to overflow lip 13 and extends along the succession of cells for removal of froth forming on the top of the pulp body. This skimmer is driven by a motor 38, through the intermediary of transmission 39.

An aerating gas, usually compressed air, is supplied to the machine through a header 41, and has suitable connections for delivery of such gas into the individual cells. Preferably, but not necessarily, one point of delivery is through a bottom inlet 42, 42* or 42 in the lower portion of the cell as by a conduit (not shown) interconnecting the header 41 and the inlet 42 of the cell, and other air is delivered into a hollow column 63, encompassing shaft 31, within the pulp body in the cell through a valve controlled conduit 43, or 43*. The term spitzkasten is used in the usual sense of the ore dressing art to indicate an enlarged portion of a vessel in which some form of separation is performed.

The front wall of the cells, as exemplifier by cells C and C (Figs. 1 and 2), is formed of an upper,

forwardly sloped section 44 including an end wall 46, and the section is bolted, as indicated at 47, in fluid engagement with lower section 12. The sloped section 44 and its end walls constitute an enlarged spitzkasten for cells C and C, having an overflow slat weir 90. As shown in Fig. 7, the sloped section 44 may be replaced by a vertical section 44 shown in dashed lines, which will be bolted in fluid tight engagement to lower section 12 and A rotary shaft 31, ar si or 31 the associated portions of the tank. The vertical section 44 has an overflow slat weir 96 The spitzkasten 44 may be used for cells which are performing cleaner operations, and the vertical section 44 may be used for cells which are performing rougher operations. Concentrate from the rougher cells is returned through a suitable conduit (not shown) into a normally closed opening 45 in the front of cells C and C.

The second form of cell construction and arrangement used in this type of flotation apparatus has been illustrated in Figs. 3 and 4. Cells C and C are formed by a front wall 12 having an overfiow lip 13, a rear wall 22*, and partitioning members 15 and 23 Adjoining partitioning members 23 and 15 define a feed compartment 16 for cell O and cell C has a corresponding feed compartment. Compartment 16 defined by wall 23 and partition 15 and controlled by weir gate 24 feeds cell C".

These cells are also provided with gate weirs 24 controlled by screw mechanism 25 for regulating the pulp discharge from cell to cell and have venturi outlets 26 spaced from and in proximity to the cell bottom, for passing the heavier sands from a preceding cell into a following feed compartment 16 Bowl-like liner section 28 and upstanding baffle members 29 of the type previously described are located in the bottom portion of said cells.

Each cell is provided with an aerating and agitating unit consisting of a shaft 31 journaled in bearings 32 and supported from superstructure 33 which may be an extension of superstructure 33 when the several cells are operated in continuous series. Shafts 31 are rotated by belt transmission 35 driven by motor 34 Froth forming on the surface of the pulp body in these cells is removed by a skimmer mechanism (not shown) of the type hereinbefore described.

Aerating gas is supplied to cells C and C by a header 41 into a chamber 50 defined by the housing of the bearing assembly 32 32 Additional gas may be introduced through a bottom inlet 42*. As shown in Fig. 4 the shaft 31 is hollow and is provided with intake openings 51 and gas delivered into chamber 50 enters the hollow shaft through openings 51 and descends to a lower point of discharge as will be explained in the following description. In addition, a plug 53, normally closing the upper end of shaft 31 may be removed to permit intake of atmospheric air as the aerating medium, if a pressure gas is not required in the treatment. In such event, a valve (not shown) closes escape of air outwardly through openings 51 and chamber 50.

Figs. and 6 illustrate still another form of cell arrangement, which may be utilized in the practice of the present invention. Again, in this form, the cells C and C are formed by a front wall 12 having a froth overflow lip 13*, a rear wall 22 and partitioning members 23 and defining a feed compartment for cell C while a final end wall 55 of the machine cooperates with the final partition 24 to define a discharge compartment 56 at the end of the machine.

This form of cell also utilizes a feed compartment 18 for delivery of pulp onto impeller 19 or agitator 21. Pulp discharge from each cell is controlled by an adjustable weir 24", the effective level of which is controlled by a screw mechanism Heavier sands which do not elevate to pass over the weir 24 discharge through relief opening 57 or the venturi outlets 26 which in this cell arrangement are positioned near the front and rear walls rather than centrally of the feed compartment 16*, as in the other cell arrangements.

Cells C and C also are provided with bowl-like liners 28 and a series of upstanding bafiles 29* within the liner enclosure. A rotary hollow shaft 31 journalled in a bearing assembly 32 supported from superstructure 33 which may be an extension of the superstructure33 of Fig. l, is rotated by a motor 34 driving belt transmission system Shaft 31 is hollow throughout its length and may be supplied with an aerating gas through the valve-controlled coupling 87 shown in cell C the opening 61 into bearing housing 32 or through the valvecontrolled conduit 43 or a conduit similar to conduit 43 of Fig. 2. In cell C a shaft SD, is mounted in similar manner.

A bonnet member 62, as illustrated in Fig. 6, also shown in Fig. 4, supports a hollow column 63 in depending position about shaft 31 as shown in cell C terminates in spaced relation to an annulus 64 from which a hood 65 is suspended in overhanging relation to a bladed impeller 66 mounted for conjoint rotation with shaft 31 near the overflow level of the cell. Suitable openings 67 are provided in column 63 for entrainment of pulp in the upper portion of the cell, and one or more openings 68 in the shaft provide a gas discharge into the entering pulp stream. Additional pulp is circulated into the enclosure through the gap between column 63 and annulus 64 and variations in the amount of gap are effected through adjustment of a sliding ring 69 at the lower end of column 63.

Another open-ended column or tube 70, is supported from feed conduit 18 in encompassing relation to the lower end of shaft 31. In addition to the pulp delivered through conduit 18*, additional pulp is circulated into the enclosure through a plurality of openings 71 positioned at different elevations. The portion of the shaft within the enclosure is provided with a series of agitating blades 72 positioned to direct the incoming pulp and aerating gas upwardly through the enclosure. Additional aerating gas may be provided through a bottom inlet 42 and gas descending through the shaft is dicharged through the open bottom end of the shaft as well as through openings 73 at or near the top of tube '70.

The arrangement illustrated in cell C differs substantially from the arrangement shown in cell 0. A flanged ring 75 is held in friction fit with the lower end of column 63 and acts as a cover member for a small diameter bladed impeller 76, mounted for rotation on shaft 31 The feed inlet conduit 18 of cell C carries a depending hood member 77 overhanging the impeller 19 and a hollow column 78 extends upwardly from cover 77, and terminates at its top in flanges 79 which substantially parallel the flanges 75 above impeller 76.

Gas is admitted to column 78 through the valve controlled conduit 43 and also through one or a plurality of openings 80 in the shaft. Suitable openings 81 are provided in the upper portion of column 78 for recirculation of pulp, and if desired, other openings 82 may be provided in the portion of the column adjoining impeller 19. Discharge passages 83 are provided at the lower end of the shaft for delivery of pulp onto the upper surface of impeller 19, and additional gas at lower end of the hollow shaft is free to pass through the open end and travel along the bottom of the impeller. Additional gas may be supplied underneath the impeller through the bottom inlet 42*. A series of agitating vanes 85, preferably formed of rubber, are mounted on the shaft adjacent the feed conduit opening and are arranged to direct the pulp and gas within column 78, and also delivered through feed conduit 18 directly onto the impeller. Final discharge of pulp from compartment 56 passes through an outlet 8 and may be passed to waste or subsequent treatment.

In addition to the aerating arrangements thus far described, a given cell may have an upper impeller unit, such as the impeller 66 of cell O, or the impeller 76 of cell C and no agitating blades, such as the vanes 85, and no lower impeller, such as the impeller 19. Rotation of shaft 31 will serve to keep sands in the lower portion of the cell in a loose condition, while sufiicient air may be introduced through the discharge outlets at the lower end of the shaft to have the lower agitator function as an air lift unit.

Likewise the rate of rotation of shaft 31 may be varied ArK4AAA M4 4.4 r r r in such an arrangement as the upper impeller actsonly on material in suspension,- and therefore is primarily a mixer or aerator. the lower unit will function as an air lift, since suflicient agitation will be provided to keep sands tending to settle in an essentially loose condition.

The multiple gas introduction arrangement of the machine permits selection control of the quantity of gas introduced at different levels in the cells, and also .permits use of gases of different composition. In addition to the points of introduction previously described, gas may be introduced as shown in Fig. 6 into the upper end of shaft 31 through the valve-controlled inlet 87, or into bonnet 62 through an opening 88.

Additional control features of themachine have been illustrated in Fig. 7 and are applicable to any of the cells of the series. Where the enlarged spitzkasten arrangement is utilized, I prefer to mount a slat weir 90 to permit a variation in overflow level depending on the depth of froth in a given cell.

Preferably, the back wall 22 of the machine also has the dual-section arrangement, so that, if desired, an enlarged spitzkasten similar to 44 may be installed on the rear wall, as well. Also a return opening 45, which is normally plugged, may be utilized for return of concentrate through the rear wall 22 such .as in cell C and C.

One of the important control features of the machine has been illustrated in Fig. 7. Openings 96 are located in the wall at the opposite side of the feed conduit 17 r to permit discharge of pulp from the feed compartment into the following cell without passing through conduit 17. These openings may be left fully open, or may be partially plugged, as indicated at 91. A gate 92 is mounted for slidable up and down movement under control of suitable mechanism 93 to vary the effective size Even at a reduced rate of rotation,

of the opening into conduit 17 and thus cause more or less of the pulp in the feed compartment to pass through openings 26. s

I also prefer to have the wall 15 or any similar wall constructed as shown in Fig. 7. Such a wall has a cut out opening 94 throughout a substantial part of the area of the cell, and normally covered by a member 95, normally bolted against the wall covering said opening, in the manner shown. When it is desired to convert the machine to an open-cell or hog-troug type, the boltedon section is removed, thus permitting the direct flow of pulp through the machine. In such event, the weir gates are positioned to permit a maximum flow from a preceding cell to a succeeding cell.

With this understanding of the general arrangement of the machine, the operation thereof will now be described in some detail. For purposes of this description it will be assumed that the machine'comprises six cells in series, of which cells C and'C are the land 2 cells, respectively; cells C and C are the 3 and 4 cells, respectively; while cells C and C are the 5 and 6. cells, respectively of the machine. This arrangement will utilize four cells as rougher cells, namely, cells C, C C and C while C and C will be cleaner cells and on that account will utilize the enlarged spitzkasten feature previously described.

Pulp is fed through a suitable opening in end wall 14 into the initial feed compartment 16 and thence passes into the feed inlet conduit 17 and is delivered thereby into the enclosure for the lower impeller member of cell C, which in this case will be assumed to use the aerating arrangement shown in cell C of Fig. 6. Aerating gas is delivered through the hollow shaft onto the upper surface of the'impeller 19 through openings 83 and other gas escapes from the hollow shaft through openings 80 and, mixes with recirculating pulp admitted through openings 81. Streams of pulp flowing through'the feed inlet conduit and down the upright column are first acted on by the vanes 85 on the rotary shaft and the resulting mixture is subjected to further aeration and mixing on the impeller surface. At the same time, additional aerating gas may be introduced through the bottom inlet 42 and mixes with pulp being swept along the bottom by the vanes on the under surface of the impeller. Due to the inclination of the under surface of the hood member 77 covering the impeller and the location of the baflles 29 adjacent the periphery of the impeller, the streams of pulp traveling outwardly along the upper and lower impeller surfaces are brought into converging relation and broken up by impact with the battle structure.

This action serves to rupture any large bubbles that have formed in the initial mixing; and as a result, the gas is finally dispersed through the circulating pulp and rises to the surface in fine bubble formation. In the upper surface of the pulp body, lines not in free floating condition normally collect and tend to build up a relatively high density zone in the pulp body which impedes the travel of aerated mineral into the froth body on the surface. In order to prevent the density increase and to render such slime portion of the pulp freely floatable, a portion of this material is recirculated into the upper portion of the hollow column mixed with additional air introduced either through the bonnet opening 88, or downwardly through the hollow shaft and finally subjected to the mixing and circulating influence of impeller 76. The discharge of the impeller 76 is essentially centrifugal, but is given a downward component due to the shaping of the members 75 and 79. As a consequence .of this, the aerated pulp travels a considerable distance towards the walls of the cell and thereby sets up a circulation tending to cause the column of aerated mineral to move near the walls of the cell, leaving non-floated material in proximity tothe central column.

Concentrate from the rougher cells may be introduced into cell C and C through the openings 45 at the front of the cell, or through similar openings 45 at the rear of the cell (Fig. 7). Since this product has already been once floated, it is essentially ready for additional flotation and requires only circulatory movement, plus additional aeration. Such aeration is provided by the streams of material combining on the bathe structure. However, any portion of this concentrate, which only moves into suspension but does not float, will be entrained in the recirculating pulp streams and thence receive the required aeration and additional impelling movement to effect flotation.

The froth forming on the surface is moved towards lip 13 by the impelling influence of scrapers 37 and is finally discharged across the lip by contact with the scraper structure and falls into a launder .(not shown), or other suitable receptacle. The provision of the slats in the upper section .4 of the front wall permits a.

selective elevation for the froth overflow. The pulp level in the cell is determined by" the effective elevation of overflow weir 24, which is set by control mechanism 251' 24 and into the feed compartment 16 of cell C. Unfloated solids pass out of cell C through opening 57into the following feed compartment or by-pass the feed compartment and travel directly through the venturi opening 26 from cell C to cell C. The same treatment is performed in cell C, except for variations in the aerating action. For the purposes of this description, it will be assumed that the aerating arrangement of cell C is essentially the same as illustrated in cell C (Fig. 6).

Consequently, pulp delivered into feed compartment 16 enters the feed inlet conduit 18 of this form and is delivered thereby into the tubular enclosure '70. Aeration within this enclosure is provided by the discharge through the open end of shaft 31 and by the inletconduit 42 The'blades 72 exert an upward cam ponent of movement to the entering pulp and together with the aerating gas exerts an air lift effect, which draws The pulp discharge from cell C passes across weir pulp from adjacent the bottom into said enclosure and discharges it outwardly from its upper end.

The location of the upper impeller 66 and its cover 65 serves to impart a downward and outward component to recirculating pulp fed thereto, and thus provides a current control which causes the aerated pulp discharge of enclosure 76 to travel outwardly and upwardly to reach the surface. Due to the spacing of the members 64 and 69, impeller 66 can be utilized to do more or less pumping as required in effecting the desired recirculation in the upper portion of the cell, and a selected degree of aeration in conjunction with this action is permitted through the control of the air introduced into bonnet 62 or into the outer shaft 313. Final discharge from cell C passes into a feed compartment (not shown), similar to compartment 16', by overflow of a weir (not shown), similar to weir 24. Cells C and C being used for rougher operations, require a considerable amount of circulatory movement and a lesser amount of aeration, and on that account preferably employ aerating arrangements of the type shown in Fig. 7 and previously described herein.

The final discharge from cell C passes over a weir 24 and enters a feed compartment 16'", which supplies cell C (Fig. 6). While the entire aerating assembly has been illustrated in Fig. 6, it usually will be preferable in the No. cell at least of the machine of the type now being described to omit the blades '72 in the lower enclosure and to utilize rotation of shaft 31 to loosen the body of material within the enclosure and allow it to be moved upwardly solely by the air lift action previously described. It should also be understood that Where too intense agitation is produced by the upper impeller 66, this member also may be omitted, particularly where brittle froths are being formed adequate elevating movement can be provided by the air lift action alone, and any solids settling out of suspension will be passed to the following cell through the venturi outlets 26*.

While the preceding description sets forth a preferred arrangement of structural features in a typical six-cell machine, it will be apparent that features shown as equivalent in function may be selected for combination in a variety of assemblies. For example, the shafts may be rotated at different speeds and by introduction of a sufficient volume of air at suitable velocity, the shafts may function as air lifts. In such operation the rotation is employed primarily to keep sands from settling and the upper impeller may be omitted, if desired. Such an operation is particularly effective in the treatment of coarse pulps.

What is claimed is:

1. In a multi-cell froth flotation machine of the type having a series of upright partitions dividing its interior into a plurality of treatment cells and aerating and pulp circulating means in each cell for the progressive movement of pulp through the succession of cells, the improvement which comprises at least one constricted, tubular passage extending through a partition adjacent a corner of the cell, said passage being adjacent the bottom of the cell and in substantially the horizontal plane of the pulp circulating means in the next successive cell for inducing circulation of nonfioated solids from one cell directly into the next said cell independently of the normal circulation in the cell.

2. In a multi-cell froth flotation machine of the type having a series of upright partitions dividing its interior into a plurality of treatment cells and aerating and pulpcirculating means in each cell for the progressive movement of pulp through the succession of cells, the improvement which comprises a constricted tubular passage arranged to provide a venturi effect extending through at least one said partition at a point remote from the normal pulp fiow adjacent the forward and rear ends thereof and adjacent the bottom of the machine in the horizontal plane of the pulp circulating means of the next succeeding cell so as to induce circulation of non-floated solids from the corners of one cell directly into the next cell in the series independently of the normal circulation in the cell.

3. In a flotation machine of the type having a feed compartment defined by end walls of adjoining cells and with the lower portion of one said wall common to both cells and a feed conduit extending from the feed compartment to a point of discharge adjacent the impeller in the following cell, the improvement which comprises at least one submerged opening extending from the feed compartment into the succeeding cell in spaced relation to said feed conduit in the horizontal plane of the impeller in said succeeding cell.

4. In a flotation machine of the type having a feed compartment defined by end walls of adjoining cells and with the lower portion of one said wall common to both cells, and a feed conduit extending from the feed compartment to a point of discharge adjacent the impeller in the following cell, the improvement which comprises a plurality of submerged openings extending from the feed compartment into the succeeding cell in spaced relation to said feed conduit in the horizontal plane of the impeller in said succeeding cell.

5. In a flotation machine of the type having a feed compartment defined by end walls of adjoining cells and with the lower portion of one said wall common to both cells, and a feed conduit extending from the feed compartment to a point of discharge adjacent the impeller in the following cell, the improvement which comprises a plurality of submerged openings extending from the feed compartment into the succeeding cell in spaced relation to said feed conduit in the horizontal plane of the impeller in said succeeding cell, and means associated with said openings for varying the discharge capacity of said opening.

6. In a flotation machine of the type having a feed compartment defined by end walls of adjoining cells and with the lower portion of one said wall common to both cells, and a feed conduit extending from the feed compartment to a point of discharge adjacent the impeller in the following cell, the improvement which comprises at least one submerged opening extending from the feed compartment into the succeeding cell in spaced relation to said feed conduit in the plane of the impeller in said succeeding cell, and at least one submerged opening between the preceding cell and the succeeding cell at a point exteriorly of the feed compartment.

7. In a flotation machine of the type having a feed compartment defined by end walls of adjoining cells and with the lower portion of one said wall common to both cells, and a feed conduit extending from the feed compartment to a point of discharge adjacent the impeller in the following cell, the improvement which comprises at least one submerged opening extending from the feed compartment into the succeeding cell in spaced relation to said feed conduit in the plane of the impeller in said succeeding cell, at least one submerged opening between the preceding cell and the succeeding cell at a point exteriorly of the feed compartment, and means associated with the feed conduit for varying the amount of pulp admitted thereto from the feed compartment.

8. In a flotation cell having an upper overflow for froth, a pulp outlet for the cell and means for introducing pulp into the cell, the improvement which comprises upper and lower means for agitating and aerating pulp in the cell, inclusive of a rotary tube having a bottom opening in the lower portion of the cell, means for delivering an aerating gas into said tube and through the bottom opening, pulp-agitating blades mounted at the lower end of said tube and having upwardly-inclined surfaces for imparting an upward elevating movement to pulp aerated by said gaseous discharge a pulp-agitating impeller mounted on the tube above said blades for directing pulp downwardly and outwardly and for deflecting upwardly moving pulp outwardly and downwardly, and a tubular enclosure for said bottom opening and the pulp-agitating means.

9. In a flotation cell having an upper overflow for froth, a pulp outlet for the cell and means for introducing pulp into the cell, the improvement which coinprises an upright hollow shaft submerged in the pulp body in the cell, at least one tubular enclosure for the shaft, an agitator mounted on said shaft below but adjacent the pulp level in the cell, pulp deflecting means associated with a portion of the tubular enclosure adapted for directing pulp acted on by the agitator along an outward and downward discharge path, and a lower agitator on the shaft interiorly of another portion of the tubular enclosure, adapted to direct pulp upwardly toward the upper agitator.

References Cited in the file of this patent UNlTED STATES PATENTS Williams June 19, Thomas Euly 5, Kraut Aug. 11, Asselstine Aug. 2, Weinig Apr. 23, Hall Dec. 27, Daman Feb. 13, Lasseter Dec. 24, Ingalls et a1 Feb. 18, Guthrie Jan. 19, Darnan et a1. 1 Apr. 20, Daman et al Feb. 5, Logue July 8, Booth Dec. 30, 

1. IN A MULTI-CELL FROTH FLOTATION MACHINE OF THE TYPE HAVING A SERIES OF UPRIGHT PARTITIONS DIVIDING ITS INTERIOR INTO A PLURALITY OF TREATMENT CELLS AND AERATING AND PULP CIRCULATING MEANS IN EACH CELL FOR THE PROGRESSIVE MOVEMENT OF PULP THROUGH THE SUCCESSION OF CELLS, THE IMPROVEMENT WHICH COMPRISES AT LEAST ONE CONSTRICTED, TUBULAR PASSAGE EXTENDING THROUGH A PARTITION ADJACENT A CORNER OF THE CELL, SAID PASSAGE BEING ADJACENT THE BOTTOM OF THE CELL AND IN SUBSTANTIALLY THE HORIZONTAL PLANE OF THE PULP CIRCULATING MEANS IN THE NEXT SUCCESSIVE CELL FOR INDUCING CIRCULATION OF NONFLOATED SOLIDS FROM ONE CELL DIRECTLY INTO THE NEXT SAID CELL INDEPENDENTLY OF THE NORMAL CIRCULATION IN THE CELL. 